When you think of a jet ski, you think of fun under the sun – not sitting still in the water with a jet ski that won’t start due to the battery. A dead battery also kills the day of fun. There are several possible reasons your jet ski’s battery is consistently dying. In this article, we’ll break down those reasons for you.

Jet ski batteries naturally lose charge during periods of inactivity. Failure to properly store the battery during winter can also lead to permanent battery damage. Age is another factor. Jet ski batteries typically last between three and five years. Electronic issues can discharge batteries or mimic battery damage.

Whether you have a jet ski battery that keeps dying or you want to prevent these fates from befalling your jet ski’s battery in the future, you’ve come to the right place. These are the top reasons that your jet ski battery keeps dying – and what you can do about it.

5 Reasons Your Jet Ski Battery Keeps Dying 

If your jet ski battery keeps failing you, we’re here to help you figure out why. Knowing exactly why your jet ski battery keeps dying or constantly needs to be replaced can help you prevent this from happening again in the future. Follow along as we break down the top reasons that your jet ski battery keeps dying on you. 

Reason One: You’re Not Riding your Jet Ski Enough

Like car batteries, jet ski batteries can die due to inactivity. This is due to battery sulphation that occurs when the battery is not in use. This can hinder the flow of electrons within the battery. 

This is a common problem in motorized vehicles but could be a bigger issue for jet ski owners due to the smaller size of their batteries compared to car batteries. 

Due to this, jet ski batteries are more prone to dying from inactivity than car batteries. An important element to consider here is the rate at which you use a car compared to a jet ski. In the winter months, for example, you may get little use out of your jet ski due to bad weather conditions. This means you could find your jet ski battery dead the next time you want to take it out.

When you frequently use your jet ski in the summer, the battery will charge itself as the motor is running. However, when you’re not using it, the battery can lose charge over time, just as a car’s battery would. This could be a possible cause for why you’ve found your jet ski with a dead battery. To prevent this, you should regularly start your jet ski to keep the battery working or keep it on a trickle charger in your garage or at the marina or dock.

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Reason Two: You’re Overcharging Your Jet Ski Battery 

Many jet ski users are not aware that it is possible to overcharge a jet ski’s battery.

Overcharging a jet ski battery, or even charging it at the incorrect charge rate, can have damaging effects on the battery. Overcharging could even lead to overheating the battery and causing certain components therein to melt. 

As mentioned above, jet ski batteries can lose charge during winter months or periods of inactivity. When charging them during these months, caution should be taken not to overcharge them. You wouldn’t want to ruin your summer plans before summer comes around! To prevent this, you can look into buying a smart charger to prevent this type of damage from happening to your jet ski’s battery – we discuss this in reason three, too. 

Reason Three: You’re Not Storing Your Jet Ski’s Battery Properly During Winter 

As discussed above, jet ski batteries can lose charge over the winter months due to inactivity. This is more likely to be the case when you are not properly storing your battery during these months of no use. You cannot simply leave the battery in the jet ski when you are not regularly using it. 

Therefore, you should make sure that you properly store your battery during the winter. By doing this, you can extend the lifespan of your battery and ensure it’s ready for you when the weather gets better, and you can take it out on the water again. 

To store the battery, you’ll need to remove it from the jet ski’s hull and store it in a dry environment that’s about 60 degrees Fahrenheit or 15 degrees Celsius. Keep your battery on a low output trickle charger. I use the Battery Tender Junior and Battery Tender Plus. These chargers will ensure the battery is not being overcharged while keeping them fresh and ready to go for the next season. Read more in my Jet Ski Battery Winter Storage Guide.

Battery Tender 800: My new favorite for storage

I just got 2 of these for winter 2022-23. I like it more than the Junior, mainly due to the absence of a large power brick at the plug in part of the cord. This way, no outlets have to be abandoned due to loss of access. Click on any image above or this Amazon link to see on Amazon.

Reason Four: Your Jet Ski’s Battery Needs to Be Replaced

If your jet ski battery is consistently dying on you, you might need to replace it. When it comes to the overall lifespan of these batteries, you’re looking at a range of three to five years total. However, if a jet ski battery has been damaged by other factors, such as those discussed above, the lifespan could be significantly reduced. 

If your jet ski’s battery is older than three years and is showing signs of failure, you’ll want to consider replacing the battery. It might even be possible the last battery you bought for your jet ski had some manufacturing fault or wasn’t powerful enough to adequately power your jet ski. 

This is why it is important to do research into a good battery for your jet ski. It can be costly to replace a jet ski’s battery, but not as pricey as replacing a car’s battery. However, by doing your research into a good replacement battery and knowing the various reasons that could affect the lifespan and overall health of the battery, you can make sure that the next battery you purchase lasts even longer. 

Reason Five: It’s Not Your Battery After All

Sometimes the problem isn’t the battery. There may be a whole host of other reasons that could be preventing your jet ski from starting, and they’re making it seem as though the battery is the culprit. These are a few of the other common issues that can prevent a jet ski from starting: 

  • If your jet ski’s starter relay is defective, you will not be able to power up your jet ski. The starter relay is responsible for the transfer of power from the battery’s starter motor to the engine in order to turn the jet ski on. As a rule of thumb, if you try to power your jet ski and only hear one click, it could be the starter relay that is causing problems. 
  • Often sparkplugs can be the reason a jet ski is not starting. It would be wise to keep an additional set of sparkplugs around for this type of issue in the future. 
  • Like with cars, you need to use the correct fuel for your jet ski. Failure to do this could result in the failure of your jet ski to start up. If your fuel cap is loose, the fuel could even become contaminated with water and lead to starting issues. 


When it comes down to a jet ski battery that keeps dying, there could be a number of possible explanations for this. Your jet ski’s battery could naturally be losing charge during months of inactivity, or you might even be overcharging it. The fault may even be a mechanical issue masquerading as a battery fault. By understanding the factors that have an impact on your jet ski’s battery and the reasons it’s not working as it should, you’ll be able to prevent these issues from occurring in the future.